The present invention relates to a gas burner for a hearth, in particular, for an industrial or domestic hearth, and a process for burning fuel gas with comburant gas.
The present invention is particularly well adapted to gas combustion. However, one would not depart from the scope of the present invention by using an atomized liquid fuel, possibly atomized pneumatically.
The burner according to the present invention has better performance than burners in the prior art, particularly with regard to the nitrogen oxide content of the off gases.
According to the present invention, a fuel introduction device is provided including a first means for injecting combustible fluid such as gas in the form of a jet which is substantially axial or slightly diverging with respect to the burner axis, and a second means for injecting a fluid such as gas in the form of a second jet diverging with respect to the burner axis.
The hearth burner according to the present invention has a primary gun for introducing a primary comburant i.e. a combustion-supporting substance, a secondary gun for producing a secondary comburant, a device for introducing a fluid fuel, particularly a gaseous fuel, and a baffle-stabilizer located essentially at the end of the primary gun facing the hearth.
A fuel introduction device can be mounted inside the primary gun which itself may be located inside the secondary gun, with the primary gun, secondary gun and fuel introduction device being cylindrical and coaxial.
The fuel introduction device may have an injector which itself has a first series of orifices forming the first fluid injection means and a second series or orifices forming the second fluid injection means. The injection axis of each of the orifices of the first series may form an angle .alpha. less than 15.degree. with respect to the direction defined by the burner axis. The axis or each orifice in the second series may form an angle .beta. between 40.degree. and 60.degree. with the direction defined by the burner axis.
The angle .alpha. of each of the orifices of the first series may be between 10.degree. and 15.degree., preferably 12.5.degree.. The angle .beta. of each orifice in the second series may be substantially approximately 50.degree..
The axis of the orifices of the first series may be substantially inscribed on the surface of a cone or a cylinder. Thus, the first jet will have substantially the shape of frustroconical sheet.
The axes of the orifices of the second series may also be substantially inscribed on the surface of a cone. Thus, the second jet will also have substantially the shape of the second jet will also have substantially the shape of frustroconical sheet.
At its end leading into the hearth, the secondary gun may have a converging section designed to direct the secondary comburant toward the primary comburant.
The fuel introduction device may comprise a pipe at the end of which the first and second gas injecting means may be attached.
The present invention also relates to a process for burning comburant gas, such as oxygen, with the fuel gas such as natural gas. The comburant gas is introduced into the hearth in at least two streams, one being central and the other surrounding this central stream.
According to the process according to the invention, two fuel gas jets are produced, with one of the jets supplying the central comburant gas stream and the other jet supplying the other comburant gas stream.
According to one important aspect of the present invention, the axial or slightly diverging jet and the diverging jet do not interfere with each other when leaving the injector and retain their individuality at this point. This can be achieved in particular by having diverging jets surround the slightly diverging axial jet.